I dont know if it is related to this mod or thermal dynamics anyway this is the crash log

Description: Ticking memory connection

java.lang.ClassCastException: mods.railcraft.common.blocks.machine.beta.TileBoilerTankHigh cannot be cast to cofh.thermaldynamics.block.TileTDBase
at cofh.thermaldynamics.block.BlockTDBase.isSideSolid(BlockTDBase.java:53)
at com.stuntmania.placeableitems.handler.RightClickHandler.rightClick(RightClickHandler.java:163)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_949_RightClickHandler_rightClick_PlayerInteractEvent.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:138)
at net.minecraftforge.event.ForgeEventFactory.onPlayerInteract(ForgeEventFactory.java:100)
at net.minecraft.server.management.ItemInWorldManager.func_73078_a(ItemInWorldManager.java:353)
at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:556)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:60)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:9)
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212)
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)

Appears to be a ThermalDynamics issue.

@magnus97 I think you should report this to the dev of placeable items.